A vehicle control system that sequentially determines target traveling positions based on the actual traveling position of a master work vehicle and navigates a slave work vehicle toward the target traveling positions is known from Patent Document 1. In this vehicle control system, control modes are disclosed, such as one in which the slave work vehicle is controlled to follow the master work vehicle so as to maintain offset amounts in X (longitude) and Y (latitude) directions set for the master work vehicle, and one in which the slave work vehicle is controlled to follow the master work vehicle, using a traveling route that is obtained by translating a traveling track of the master work vehicle by the work width as a target traveling route. Here, the traveling positions of the work vehicles are acquired using GPS (Global Positioning System). A technique for controlling unmanned navigation of a tractor based on traveling position information using GPS is described in detail in Patent Document 2.
The following control of Patent Document 1 is intended for work performed on work ground with a large area, rather than for traveling in a complicated route on work ground such as a field with a relatively small area that is bounded by a ridge or the like. In work traveling performed on such a field and the like, it is necessary not only to perform redirection of 180 degrees or 90 degrees but also to repeatedly perform traveling-system operations such as deceleration, acceleration, stopping, and starting. Furthermore, depending on the type of work traveling, it is also required to repeatedly perform work-system operations such as driving and stopping of a work implement, and raising and lowering of the work implement. For example, rice or wheat reaping work in a small agricultural field is performed using back and forth traveling in which vehicles travel while repeatedly performing straight work traveling and U-turns in the central area of the agricultural field, and loop traveling in which the vehicles perform work while traveling in a loop in a loop work area, which is defined as the perimeter of the U-turn work area. Accordingly, the agricultural field is divided in advance into the U-turn work area and the loop work area, and in each of the areas, the traveling-system operations and the work-system operations are frequently performed. However, it is difficult to realize such non-simple work traveling with a conventional system for performing work and traveling on work ground with a large area using predetermined traveling-system operations and work-system operations.